1. Field of the Invention
The present invention is concerned with antimicrobial compositions which are useful for inhibiting microbial growth wherever such microbial growth is undesirable, e.g., aqueous systems found in a variety of industrial applications, such as papermaking.
In particular, the present invention is concerned with antimicrobial compositions which comprise a synergistic mixture of two components. One component is a polyether polyamino methylene phosphonate, which has also been found to exhibit excellent calcium carbonate scale inhibition under the severe conditions of high calcite concentration and high pH which characterize, e.g., a cycled up cooling tower. Thus, control of unwanted microbial growth in such systems is provided in addition to scale control; however, the present invention is not limited to such applications.
The other component of the synergistic mixture is a non-oxidizing biocide, which is one or more members selected from the group consisting essentially of those detailed further herein. All of these non-oxidizing biocides, as well as combinations thereof, are well known in the antimicrobial art. However, the discovery that these conventional non-oxidizing biocides could form the basis for synergistic combinations with the polyether phosphonates described herein, was both surprising and unexpected.
As used herein, the phrases, "antimicrobial" and "inhibiting microbial growth" describe the killing of or destruction of, as well as the inhibition of or control of the growth or propagation of bacteria, fungi (including yeasts and molds) and algae in dormant, immature developing and/or mature stages. A number of important industries can experience serious adverse effects from the activity of such bacteria and fungi on the raw materials which they employ, on various aspects of their manufacturing activities, or on the finished products which they produce. Such industries include the paint, wood, textile, cosmetic, leather, tobacco, fur, rope, paper, pulp, plastics, fuel, oil, rubber, and machine industries. Important applications of the synergistic antimicrobial combination of the present invention include: inhibiting the growth of bacteria and fungi in aqueous paints, adhesives, latex emulsions, and joint cements; preserving wood; preserving cutting oils; controlling slime-producing bacteria and fungi in pulp and paper mills and cooling waters; as a spray or dip treatment for textiles and leather to prevent mold growth; as a component of anti-fouling paints to prevent adherence of fouling organisms; protecting paint films, especially exterior paints, from attack by fungi which occurs during weathering of the paint film; protecting processing equipment from slime deposits during manufacture of cane and beet sugar; preventing microorganism buildup and deposits in air washer or scrubber systems and in industrial fresh water supply systems; controlling microorganism contamination and deposits in oil field drilling fluids and muds, and in secondary petroleum recovery processes; preventing bacterial and fungal growth in paper coating processes which might adversely affect the quality of the paper coating; controlling bacterial and fungal growth and deposits during the manufacture of various specialty boards, e.g., cardboard and particle board; preventing sap stain discoloration on freshly cut wood of various kinds; controlling bacterial and fungal growth in clay and pigment slurries of various types which are manufactured for later use in paper coating and paint manufacturing for example, and which are susceptible to degradation by microorganisms during storage and transport; as a hard surface disinfectant to prevent growth of bacteria and fungi on walls, floors, etc.; and in swimming pools to prevent algae growth.
The control of bacteria and fungi in pulp and paper mill water systems which contain aqueous dispersions of papermaking fibers is especially important. The uncontrolled buildup of slime produced by the accumulation of bacteria and fungi causes offgrade production, decreased production due to breaks and greater cleanup frequency, increased raw material usage, and increased maintenance costs. The problem of slime deposits has been aggravated by the widespread use of closed white water systems in the paper industry.
Another important area where control of bacterial and fungal growth is vital is in clay and pigment slurries. These slurries are of various clays, e.g. kaolin, and pigments, e.g. calcium carbonate and titanium dioxide, and are manufactured usually at a location separate from the end use application, in for example, paper coating and paint manufacturing, and are then stored and held for later transport to the end use location. Because of the high quality standards for the paper and paint final products in which the slurry is used, it is essential that the clay or pigment slurry have a very low microorganism count or content so that it is usable in the paper coating or paint manufacturing.
Yet another important area for controlling microbial growth is cooling systems such as those using cycled up recirculating cooling towers. Such systems maintain a large body of water for a considerable length of time exposed to the atmosphere under conditions which do not include sufficient aeration and exposure to sunlight to provide control of microbial, especially bacterial and fungal, growth. In particular, many cooling towers use fill composed of beads of synthetic polymer or other materials, in order to extend the amount of heat exchange surface area, and this type of construction greatly aggravates the problem of microbiological growth, since it provides an ideal physical environment for the propagation of troublesome microbes. Unchecked, such microorganisms flourish and produce colonies extensive enough to give rise to problems of biofilm blockage of heat exchange surfaces, as well as clogging of the components of the water transporting apparatus used in operating the cooling system. The synergistic combinations of the present invention provide not only excellent control of microbial growth in such systems, but also inhibit the deposition of calcium carbonate scale as well.
The synergistic combination of the present invention has been found especially useful in controlling the harmful effects of microorganisms in water or aqueous media. Systems which utilize circulating water or aqueous media become infected with microorganisms and experience substantial impairment of their efficiency when deposits of the microorganisms build up in the system. The deposits, called slimes, coat the walls of tanks and other vessels, and any machinery or processing equipment which is employed, and create blockages in pipes and valves. The slime formation promotes corrosion of metal surfaces and facilitates the deterioration of wooden towers. The slimes also create discolorations and other imperfections in any products being produced, forcing costly shutdowns. Control of microorganisms in aqueous media is particulary important where there are dispersed particles or fines in the aqueous media, e.g., dispersed cellulosic fibers and dispersed fillers and pigments in papermaking, and dispersed pigments in paint manufacture.
The synergistic antimicrobial combination of the present invention may also be utilized for agricultural and animal health applications, for example in preventing or minimizing the growth of harmful bacteria, yeast, and/or molds on plants, trees, fruit, seeds or soil. The synergistic combination may be useful in treating seed to prevent microorganism, particularly fungal attack. The synergistic combination may also be useful in protecting animal dip compositions against the buildup of microorganisms, and for this purpose may be combined with a veterinary animal dip parasiticide and an acceptable carrier.
2. Brief Description of the Prior Art
Grief, et al., U.S. Pat. Nos. 3,833,731 and 3,877,922; and Hatmetz et al., U.S. Pat. Nos. 3,873,597 describe 2-bromo-2-bromomethyl-glutaronitrile and related compounds and their use as antibacterial, antifungal and algicidal agents.
Hinton et al. U.S. Pat. No. 3,065,123 describes a process for controlling microorganisms in water and aqueous media by the addition of certain 1:2-benzisothiazolones.
British Pat. No. 1,531,431 describes treatment with N-alkyl 1,2-benzisothiazolin-3-ones for controlling microorganisms in water-based paints and adhesives, water-oil emulsions, and metalworking fluids.
Gazzard et al. U.S. Pat. No. 3,970,755 describes biocidal compositions comprising certain quaternary ammonium compounds and 1,2-benzisothiazolin-3-ones.
U.K. Pat. No. 1,458,041 describes a synergistic biocidal composition, especially for aqueous systems, containing isothiazolin-3-ones and 2-thiono-tetrahydro-1,3,5-thiadiazines.
U.S. Pat. No. 4,604,405 discloses synergistic antimicrobial admixtures of 2-bromo-2-bromomethyl-glutaronitrile and 2,2-dibromo-3-nitrilopropionamide.
U.S. Pat. No. 4,612,328 discloses synergistic antimicrobial admixtures of 2-bromomethyl-glutaronitrile and methylene bis(thiocyanate).
U. S. Pat. No. 4,655,815 discloses synergistic antimicrobial admixtures of 2-bromo-2-bromomethyl-glutaronitrile and a formaldehyde donor.
U.S. Pat. No. 4,830,657 discloses synergistic antimicrobial admixtures of 2-bromo-2-bromomethyl-glutaronitrile and 1,2-benzisothiazolin-3-ones.
However, there is no suggestion in any of the above references of the synergistic antimicrobial combination of the present invention.